Construction of dynamoelectric machines



Sept. JOHNS ETAL CONSTRUCTION OF DYNAMOELECTRIC MACHINES Filed May 16, 1950 2 SHEETSSHEET 1 42 I3 T \4 so 5r s4 35 3 3 11 28 348 46 4| l 53 L1 00 I '2 h z 4 E 25 43 \44 I7 3% 48/: 45 4 5 5 49 .L 26 as J n I 20 a9 31 32 3 IH'. I F|g.l.

WITNESSES: IIZJJVESJTSRSB Francis 0 ns W Henry J. Owens.

- BY 7 2w.

ATTOR EY Sept. 16, 19 F. J. JOHNS EI'AL 2,

I CONSTRUCTION OF DYNAMOELECTRIC MACHINES Filed May 16, 1950 2 SHEETS-SHEET 2 WITNESSES: INVENTORS Frc mcis J. Johns 8 W Henry J. Owe'ns.

BY' 7&0. A. F p

ATTO EY Patented Sept. 16, 1952 CONSTRUCTION OF DYNAMOELECTRIC MACHINES Francis J. Johns and Henry J. Owens, Buffalo,v N. Y., assignors to Westinghouse Electric (1011- poration, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 16, 1950, Serial N0. 162,368

9 Claims.

The present invention relates to the construction and ventilation of dynamoelectric machines, and more particularly toa construction for a motor-generator set which is, capable of being used as either a water-cooledv machine or an aircooled machine, and which is readily adaptable for either type of operation by means of the addition or. omission of a relatively few parts.

The construction of the present invention is especially suitable for motor-generator sets consisting of an electric motor driving a highfrequency alternator, usually of the inductor type, for supplying high-frequency alternating current. Such sets are frequently used for supplying induction heating equipment, or other equipment where high-frequency current is required. Both water-cooled and air-cooled motor-generator sets of this type have been built, and both types are extensively used. As designed and built heretofore, however, these two types of machines have been ofentirely different construction, and have had practically no parts in common. This; has meant that water-cooled and air-cooled high-frequency motor-generator sets have had to be designed and built as different, and more. or less unrelated, types of machines, and the manufacturers of these machines have had to maintain separate stocks of different parts for the two different types of motor-generator sets, with corresponding high cost.

The principal object of the present invention is to provide a construction for motor-generator sets which is suitable for operation with either water-cooling or air-cooling, and which can readily be adapted for either type of cooling by the addition or omission of a relatively few parts inthe final assembly of the machine. This construction materially simplifies the design and manufacture of these machines, and greatly reduces the number of different parts which must be manufactured and stocked, thus reducing the cost of the machine. 7

Another object of the invention is to provide a motor-generator set having a motor and a generator mounted in a common. frame structure, with means for circulating ventilating air in separate paths through the generator and motor within the frame structure, the frame structure being adaptable for operation as either a watercooled or an air-cooled machine by adding or omitting a relatively few parts in. the final assembly of the machine.

A further object of the invention is to provide an air-cooled motor-generator set in which air is admitted at opposite ends of a common frame structure, flows in separate paths through the motor and generator, and is discharged through openings near the center of the frame.

.Still another object of the. invention is to provide a water-cooled motor-generator set in which air is circulated in separate paths within the frame through the motor and generator and over cooling coils located in housings attached to the opposite ends of the frame.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawings, in which Figure 1 is a view, partly in elevation and partly in. longitudinal section, showing a watercooled motor-generator set embodying the invention;

Fig. 2 is a view, partly in elevation and partly in longitudinal section, showing a motor-generator set of the same construction adapted for air-cooled operation;

Fig. 3 is a transverse sectional view through the generator end of the machine, approximately on the line IIIIII of Fig. 1, and

Fig. 4 is a transverse sectional view through the motor end of the machine, approximately on the line IVIV of Fig. 1.

The invention is shown in the drawing embodied in a motor-generator set consisting of a generator I and a motor 2 supported in a common frame structure 3. As indicated above, the construction of this motor-generator set is such that it can readily be adapted for operation with either Water-cooling or air-cooling, the frame structure, and the motor and generator themselves, being the same for either type of operation. The common frame structure 3 is generally cylindrical and is closed at the ends by suitable end members 4. The end member 4 at the left-hand, or generator, end of the machine has two sets of circumferentially disposed, radial- 1y spaced openings 5 and 6 formed therein for the passage of ventilating air, and the end member 4 at the right-hand, or motor, end of the machine has two. similar sets of radially spaced openings 1 and 8. Larger openings 9 for the passage of ventilating air are disposed circumferentially of the frame structure 3 near the center. A common shaft In for both the motor and generator extends through the frame. structure 3 and is supported in bearings ll, of any suitable type, mounted in the end members 4.

The generator I is shown as being an inductor type high-frequency g nerator, and has a stator core member 12 mounted in the frame structure 3. As shown in Fig. 3, the generator stator core [2 is generally square in outside configuration, with rounded corners, and is pressed or otherwise secured in a frame ring I 3, which in turn is mounted directly in the frame structure 3, by pressing or otherwise. The generally square configuration of the stator core !2 forms large axial air ducts hi extending between the frame 3 and the sides of the core 12, between the corners of the core. If desired, the straight sides of the core I2 may be provided with grooves l5 to increase the surface area exposed to the ventilating air flowing through the ducts it, although these grooves may not always be necessary and may be omitted if not needed. The generator stator core has a plurality of slots :6 in its inner periphery, in which the stator winding l? is disposed, and a directcurrent exciting winding [8 is placed in larger slots suitably disposed in the stator core I2. The generator 1 also includes a laminated rotor member is mounted on the shaft liland having a plurality of axial air passages 29 extending through it. If desired, the axial air passages may also have grooves 2| to increase the surface area exposed to the flow of air. The rotor I9 carries no windings but has teeth 22 on its outer periphery, so that when the rotor is rotated, the reluctance of the magnetic path of the flux produced by the exciting winding 53 is varied, causing a pulsation of the flux to generate a highfrequency alternating current in the stator winding Ii. A conical sheet metal baflie 23 is secured to the left-hand end member 4 between the openings 5 and 6, and extends close to the rotor 19 to direct air flowing through the openings 5 and 6 in the desired paths, as explained hereinafter.

The motor 2 is shown as being a more or less usual squirrel-cage induction motor. The motor has a laminated stator core 25 which carries the primary winding 23. The core 25 is supported in the frame structure 3 by means of a plurality of radial ribs 2'! welded or otherwise suitably secured to the frame structure 3, so that the outer periphery of the core 25 is radially spaced from the frame structure 3. Longitudinal barrier members or bafiles 28 are supported on the ribs 27 in the spaces between the core 25 and the frame 3. These barrier members extend'longi tudinally for the entire length of the motor, and extend circumferentially between adjacent ribs 27, sothat the spaces between the core 25 and frame'@ are dividedinto radially, inner and outer longitudinal air ducts 29 and 39, respectively. The motor 2 has a laminated rotor member 31 mounted on the shaft It and carrying a suitable secondary winding, shown as a squirrel-cage winding 32. The motor 3| may, if desired, have axial air passages 33 extending through it. A conical sheet metal baffle 34 is secured to the ends of the barrier members 28 at the outside end of the motor and extends close to the end member 4 at that end, as shown, to separate and direct the streams of air flowing through the openings 1 and 8. A similar conical baiile 35 is secured to the other ends of the barrier members 28 adjacent the center of the machine, to direct air flowing through the ducts 29 and 3B.

Ventilating air is circulated in separate paths through the motor and generator, through the various air ducts and passages mentioned above, by means of a fan means or blower 36 mounted on the shaft iii in the center of the machine between the generator and the motor. The fan means 36 consists of a disk member 31 mounted directly on the shaft in, with a set of fan blades 38 on the generator side for circulating air through the generator, and a second set of fan blades 39 on the motor side for circulating air through the motor. It will be noted that the baffle 35 extends close to the outside of the fan blades 39 so as to direct air flowing through the inner ducts 23 directly into the fan. The openings 9 in the frame structure 3 are located directly opposite the fan means 36, so that air discharged from both sides of the fan can escape through these openings when the machine is operating as an air-cooled machine, as more fully described hereinafter.

The machine as so far described embodies the basic construction of the new motor-generator set, and all the parts thus far described are common to the machine when used with either air-cooling or water-cooling. Thus, it will be seen that only a single design of the major components of the machine is required for either air-cooled or wateroooled operation, and the same basic construction is readily adaptable for either use.

Fig. 1 of the drawings shows the machine arranged for water-cooling. For this purpose a sheet steel housing 40 is secured to the generator end of the machine and a similar housing ii is secured to the motor end of the machine, the housings 43 and 4! being placed on the outside of the end members i. The housing it contains a cooling coil @2, which is preferably made of finned copper tubing arranged to cool air flowing over it, and which has end portions 43 extending out of the housing 40 for the entrance and discharged cooling water. The housing 49 also contains a cylindrical bafile 44, directly under the cooling coil, to cause air entering the housing through the openings 6 to flow through and over the cooling coil 42, and a conical baffle 45 adapted to direct air which has passed over the coil 32 back to the openings 5. Thus, when the housing it is in place at the'end of the frame 3, over the openings 5 and 6, heated air discharged through the openings 6 will pass over the coil 42 to be cooled thereby and will re-enter the machine through the openings 5. The housing 4!, at the motor end, is similar to the housing 40, and contains a cooling coil 46 which may be identical to the coil 42, except that fewer turns may be adequate for sufiiciently cooling the air. Bailies 48 and 39, corresponding to the baffles 44 and 45, are also provided in the housing t! to direct air entering the housing through the openings 8 over the cooling coil 46 and back into the machine through the openings 1.

Besides thehousings 4B and ii, the other additional parts needed for water-cooled operation of the machine include covers 50 closing the openings 9. The covers 50 preferably are provided with a layer of sound-absorbing material SI, of any suitable type, filling the openings 9 to reduce the noise of the machine. A central baffie structure is also provided adjacent the fan means 3%. This bafile structure includes a central annular member 52, which extends close to the outer periphery of the fan disk 31, and which carries a conical baffle member 53 on the generator side and a similar bafile 54 on the motor side. A cylindrical bailie 55 is secured to the inner end of the generator rotor 15 and extends close to the fan 36.

In the operation of this machine, when arranged for water-cooling as described above, the air within the frame 3 is circulated in separate paths by the fan means 33 through the generator and motor and the housings 40 and 4!, the paths 5. followed by the air being generally as. shown by the arrows on the drawing. Thus, most of the air discharged from the fan blades 38 on the generator side of the fan is directed by the bafiie 53 over the stator winding I I and into the axial ducts I4 between the generator stator core and the frame and flows longitudinally through these. ducts. Some of the air flows in under the winding I1 and through the air gap between the stator and rotor. The air flowing longitudinally in this way passes through the outer openings 6 in the end member 4 and into the housing 40, where it flows over the cooling coil 42 and is cooled by water circulating through. the coil. After passing over the coil 42, the cooled air is directed by the baffle 4 5 through the openings 5 back into the frame structure 3, and is directed by the baflle 23 into the axial passages 26 in the generator rotor I9. The air flows through these passages and is directed by the cylindrical bafiie 55 back into the fan blades 38 to be recirculated.

The air discharged from the. fan blades 39. on the motor side of the fan is directed by the baffles 35 and 54 into the. outer longitudinal ducts 3B on the motor side and flows longitudinally through these. ducts, andthrough the outer openings 8 in the end member 4 at the motor end of the machine, into the housing 4i. The. air then passes over the cooling coil 46 to be cooled by water circulated through the coil, and is directed by U the bailie 49 through the inner openings l back into the machine. Part of the air thus entering the machine flows through the air gap. and through the axial passages 33. in the motor rotor 3|, while the rest of the air flows over the motor primary winding 26 and is directed by the bathe 34 into the inner longitudinal ducts 29. The air thus flowing through the ducts '29 is directed by the bafiie 35 back into the fan blades 3t to be recirculated, while the air flowing through the air gap and rotor passages passes directly into the fan. Thus, it will be seen that the air in the machine is circulated in closed, separate paths through the motor and generator, and over the cooling coils in the housings 40' and 4!.

When air-cooled operation is desired, the housings 4!) and II, the covers 58, baiiles 52, 53 and 54, and the bafile 55' are omitted, as shown in 2, and a conical baille 58 is secured to the frame on the generator side of the fan closely adjacent the openings 9. The baiile 56 extends close to the outer periphery of the generator fan blades. 38. In the operation of this machine with air-cooling, air enters through the end members 4 at both ends of the machine and is discharged through the openings 9 near the center of the frame, as shown by the arrows in Fig. 2. Thus, the generator is cooled by a stream of air entering through the inner openingsi in the end member 4 and directed by the baffle 2.3 into the passages 20 in the rotor, and also by a stream of air entering through the outer openings 6 and flowing through the ducts I 4- and over the stator windings I1, and through the air gap. The air flowing through the rotor passages 20 flows directly into the fan 38, while air flowing through the ducts i4 is directed by the baflle 56 over the stator winding I I and into the fan 38, the air then bei discharged radially through the openings 9. The motor is similarly cooled by air entering through the inner openings I in the end member 4 and flowing through the air gap and rotor passages, part of the air being directed by the baflle 34 over the primary winding 26 and into the inner longitudinal ducts 92. This air flows through the 6 ducts. 29 and is directed by the baffle 35 over the primary winding 26 at the inner end of the motor and into the fan 39, which discharges it radially through the openings 9.. Air also flows through the outer openings 8 and the outer longitudinal ducts 30' to the openings 9 and contributes somewhat to cooling the motor.

It will be seen that both the generator and the motor are. effectively cooled when the machine is operated with either water-cooling or air-cooling. Effective cooling of the generator is especially necessaryin machines of the type illustrated, because of the high-frequency generator currents. In the machine described, it will be noted that incoming cool air flows directly over the. bearing H at the generator end and through the ventilating passages 20 in the rotor, thus providing extremely eilective cooling for the rotor. This is important in inductor type. alternators because of the very small air gaps used. If the rotor is. notv adequately cooled, the thermal expansion of the rotor may be sufiicient to cause it to rub against. the stator. This difficulty is avoided in accordance with the present invention by directing the incoming cool air directly into the rotor air passages so that the rotor temperature rise and thermal expansion are kept small. The square configuration of the generator stator is also an advantageous feature, since it not only provides longitudinal air ducts in a simple and inexpensive manner, but it allows for some thermal expansion and deformation of the stator core Without the risk of damage. Thus, if a conventional cylindrical stator core were pressed directly into the frame 3, the core would be prevented from expanding radially, and the thermal expansion might be great enough to cause the core to buckle or become distorted and contact the rotor. By the use of a square core, however, the stator core is adequately cooled by the large air ducts and has suificient. freedom for expansion so that there is no risk of trouble clue to thermal expansion.

The construction described makes possible a motor-generator set which can readily be adapted for either air-cooled or water-cooled operation. It will be seen that the main elements of the machine are the same for either type of operation, and thatv the machine can readily be adapted for either air-cooling or water-cooling merely by the addition or omission of a relatively few elements during the final assembly of the machine. This construction, therefore, re sults in a large saving in the cost of manufacture of high-frequency motor-generator sets, since the same design is used for both air-cooled and water-cooled machines, and the problem of stocking parts is greatly reduced because of the smaller number of different parts which must be. maintained in stock, as compared to the number required by the previous practice in which water-cooled and air-cooled machines were built as entirely difierent machines of unrelated design, with practically no parts in common.

The invention has been described with particular reference to a high-frequency motor-generator set, but it will be apparent that the usefulness of the invention is not restricted to this particular application, and that it is also applicable to other types of motor-generator sets. The particular construction and arrangement of the motor and generator and of the cooling means may also be applied to individual dynamoelectic machines, either air-cooled or watercooled. It is to be understood, therefore, that although a specific construction has been shown and described for the purpose of illustration, the invention is not limited to this particular embodiment, but in its broadest aspects, it includes all equivalent embodiments and modifications which come within the scope of the appended claims.

We claim as our invention:

' 1. A motor-generator set comprising a frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, the generator and the motor each having a rotor member mounted on the shaft and each having a stator core carrying windings, said stator cores being mounted in the frame structure so as to provide axial ducts between the cores and the frame structure, fan means on the shaft between the generator and motor for circulating air in separate paths through the generator and motor and said ducts, the frame structure having radially spaced openings for air at the ends thereof and having openings for air adjacent the fan means, baille means adjacent the openings at both ends of the frame for separating the air passing through the radially inner and outer openings and directing the air in predetermined paths, the frame structure being adapted for operation as an air-cooled machine by means of a baiiie member disposed at the generator side of the fan means to direct air 9 flowing through the ducts in the generator side over the generator windiings and into the fan means, the air entering through the openings at both ends of the frame structure and being discharged through the openings adjacent the fan means, and the frame structure also being adapted for operation as a water-cooled machine means of housing members secured to the ends of the frame structure over the air openings, the housings having cooling coils therein for circula tion of water, cover means closing the openings in the frame structure adjacentthe fan means, and baffie means disposed adjacent the fan means for directing the air in the machine in closed paths through the axial ducts, the housings and the generator and motor.

2. A motor-generator set comprising a frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, the generator and the motor each having a rotor member mounted on the shaft, the generator rotor having axial air passages therethrough, the generator having a stator core carrying, windings, said stator core being substantially square with rounded corners and being mounted in the frame structure with the corners engaging the frame structure to provide axial ducts for ventilating air between the corners, the motor having a startor core carrying windings, means for mounting the motor stator core in the frame structure with its periphery spaced from the frame structure, longitudinal barrier members disposed in the space between the motor stator core and the frame structure to divide the space into two parallel, axial ducts for ventilating air, fan means on the shaft between the generator and motor for circulating air in separate paths through the generator and motor and said ducts, the frame structure having radially spaced openings for air at the ends thereof and having openings for air adjacent the fan means, baffle means adjacent the openings at both ends of the frame for separating the air passing through the radially inner and outer openings and directing the air in predetermined paths, the frame structure being adapted for operation as an air-cooled machine by means of a bailie member disposed at the generator side of the fan means to direct air flowing through the ducts in the generator side over the generator windings and into the fan means, the air entering through the openings at both ends of the frame structure and being discharged through the openings adjacent the fan means, and the frame structure also being adapted for operation as a water-cooled machine by means of housing members secured to the ends of the frame structure over the air openings, the housings having cooling coils therein for circulation of water, cover means closing the openings in the frame structure adjacent the fan means, and baflie means disposed adjacent the fan means for directing the air in the machine in closed paths through the axial ducts, the housings and the generator and motor.

3. A motor-generator set comprising a frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, the generator and the motor each having a rotor member mounted on the shaft, the generator rotor having axial air passages therethrough, the generator having a startor core carrying windings, said stator core being substantially square with rounded corners and being mounted in the framestructure with the corners engaging the frame structure to provide axial ducts for ventilating air between the corners, the motor having a stator core carrying windings, means for mounting the motor stator core in the frame structure with its periphery spaced from the frame structure, longitudinal barrier members disposed in the space between the motor stator core and the frame structure to divide the space into two parallel, axial ducts for ventilating air, fan means on the shaft between the generator and motor for circulating air in separate paths through the generator and motor and said ducts, the frame structure having radially spaced openings for air at the ends thereof and having openings for air adjacent the fan means, balile means adjacent the openings at the generator end of the frame structure for directing air flowing through the radially inner openings into the axial passages of the generator rotor and for separating said air from the air flowing through the radially outer openings and the axial ducts between the generator stator core and the frame structure, baffie means at both ends of the motor for directing air flowing through the radially inner openings at the motor end of the frame structure into the inner of said parallel ducts and for directing said air into the fan means and separating it from air flowing through the outer openings at the motor end of the frame struc ture and the outer of the parallel ducts, the frame structure being adapted for operation as an air-cooled machine by means of a bafile member disposed at the generator side of the fan means to direct air flowing through the ducts on the generator side over the generator windings and into the fan means, the air entering through the openings at both ends of the frame structure and being discharged through the openings adjacent the fan means, and the frame structure also being adapted for operation as a water-cooled machine by means of housing members secured to the ends of the frame structure over the air openings, the housings having gamete cooling coils therein for circulation of water, cover means closing the openings in the frame structure adjacent the fan means, and bafiie means disposed adjacent the fan means for directing the air in the machine in closed paths through the axial ducts, the housings and the generator and motor.

4. A motor-generator set comprising a frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, the generator and the motor each having a rotor member mounted on the shaft, the generator rotor having axial air passages therethrough, the generator having a stator core carrying windings, said stator core being substantially square withrounded corners and being mounted in the frame structure with the corners engaging the frame structure to provide axial ducts for ventilating air between the corners, the motor having a, stator core carrying windings, means for mounting the motor stator core in the frame structure with its periphery spaced from the frame structure, longitudinal barrier members disposed in the space betweenthemotor stator core and the frame structure to divide the space into two parallel, axial ducts for ventilating air, fan means on the shaft between the generator and motor for circulating air in separate paths through the generator and motor and said ducts, the frame structure having radially spaced openlugs for air at the ends thereof, bafile means adjacent the openings at the generator end of th frame structure for directing air 'fiowing through the radially inner openings-into the axial passages of the generatorrotor and for separating said airfrom the air flowing through the radially outer openings and the axial ducts between the generator stator core and the frame structure, and bafile means at both ends of the motor for directing air'fiowing through the radially inner openings at the motor end of the frame structure into the inner of said parallel ducts and for directing said air into the fan means and separating it from air flowing through the outer openings at the motor end of the frame structure and the outer of the parallel ducts.

5. A motor-generator set comprising a generally cylindrical frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, the generator and motor each having a rotor member mounted on the shaft, the generator rotor having axial air passages therethrough, the generator having a stator core carrying windings and mounted in the frame structure so as to provide axial air ducts between the core and the frame structure, the motor havinga stator core carrying windings and mounted in the frame structure so as to provide axial air ducts between the core and the frame structure, longitudinal barrier members dividing the ducts between the motor stator core and the frame structure into radially inner and outer ducts, fan means on the shaft between the generator and motor for circulating air'in separate paths through the generator and motor, the frame structure having radially spaced openings at both ends thereof, housings covering said openings, cooling coils for the circulation of water in said housings, baflle means adjacent the fan means for separating air discharged from the fan means on the generator side from air discharged from the fan means on the motor side, bafiie means for causing air discharged from the fan means on the generator side to flow through the axial ducts between the generator stator core and the frame structure, through the radially outer openings in the frame structure at the generator end into the housing at that end, overthe cooling coil in the housing, through the radially inner openings back into the frame structure, through the axial passages in the generator rotor, and into the fan means, and other baflle means for causing air discharged from the fan means on the motor side to flow through the radially outer ducts between the motor stator core and the frame structure, through the radially outer openings in the frame structure at the motor end into the housing at that end, over the cooling coil in the housing, through the radially inner openings back into the frame structure, through the radially inner ducts over the motor stator core, and into the fan means.

6. A motor-generator set comprising a generally cylindrical frame structure, an electric generator and an electric motor supported in the rame structure and having a common shaft, the generator and motor each having a rotor member mounted on the haft,-the generator rotor having axial air passage therethrough, the generator 7 avi-ng .a stator core carrying windings and mounted in the frame structure so as to provide axial air passages therethrough, the generator structure, the motor having a stator core carrying windings and mounted in the frame structure so as to provide axial air ducts between the core and the frame structure, longitudinal barrier members dividing the ducts between the motor stator core and the frame structure into radially inner and outer ducts, fan means on the shaft between the generator and motor for circulating air through the generator and motor, the frame structure having radially spaced openings at both ends thereof, housings covering said openings, cooling coils for the circulation of water in said housings, baffle means adjacent the fan means for directing air discharged onthe generator side of the fan means into the axial ducts on the generatorside, said air flowing through the ducts and through the radially outer openings in the frame structure into the housing at the generator end, means in the housing for directing the air over the cooling coil and into the inner openings in the frame structure, bafile means for directing air flowing through said inner openingsinto thegenerator rotor air passages, a cylindrical baffle on thegenerator rotor for directing air discharged from the rotor air passages into the fan means, ba-fiie means adjacent the fan means for directing air discharged from the fan means on the motor side into outer duct-s on the motor side and for directing air flowing in the opposite direction through the inner ducts into the fan means, baffle means at the other end of the motor for directing air flowing through the outer ducts into t-heradially outer openings in the frame structure and the housing at the motor end, said last-mentioned baffle means also directi g air entering through the radially inner openings at the motor end into the inner air ducts, and the housing at the motor-end having means therein for directing air entering the housing through the outer openings in the frame structure over the cooling coil and back through the inner openings in the frame structure.

7. A motor-generator set comprising a generally cylindrical frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, motor each having a rotor member mounted on the shaft, the generator ll 7 air passages therethrough, the generator having a stator core carrying windings, said generator stator core being substantially square with rounded corners and being mounted with the corners engaging the frame structure to provide axial air ducts between the corners, the motor having a stator core carrying windings, said motor stator core being mounted in the frame structure with its periphery spaced radially from the frame structure to provide axial duct spaces between the motor stator core and the frame structure, longitudinal barrier members dividing said duct spaces into radially inner and outer ducts, fan means on the shaft between the generator and motor for circulating air through the generator and motor, the frame structure having radially spaced openings at both ends thereoflhousings covering said openings, cooling coils for the circulation of water in said rotor having axial housings, baffle means adjacent the fan means for directing air discharged on the generator side of the fan means into the axial ducts on the generator-side, said'air'flowingthrough the ducts and through the radially outer openings in the frame structure into the housing at the genera tor end, means in the housing for directing the air over the cooling coil and into the inner openings in the frame structure, bafile means for directing air flowing'through said inner openings into the generator rotor air passages, a cylindrical baflie on the generator rotor for directing air discharged from the rotor air passages into the fan means, bafiie means adjacent the fan means for directing air discharged from the fanmeans on the motor side into the outer ducts on the motor side and for directing air flowing in the opposite direction through the inner ducts into the fan means, bafile means at the other end of the motor for directing air flowing through the outer ducts into the radially outer openings in the frame structure and the housing at the motor end, said last-mentioned baffle means also directing air entering through the radially inner openings at the motor end into the inner air ducts, and the housing at the motor end having means therein for directing air entering the housingthrough the outer openings in the frame structure over'the cooling coil and back through the inner openings in theframe structure.

8. A motor-generator set comprising a generally cylindrical frame structure, an electric generator and an electric motor supported in the frame structure, said generator and motor having stator cores mounted in the frame structure to provide axial air ducts between the cores and the frame structure, the ducts between the motor stator core and the frame structure being divided into radially inner and outer ducts, the generator and motor each having a rotor and at least the generator rotor having axial air passages therethrough, end members closing the ends of the frame structure, said end members having openings for the passage of ventilating air, housings at both ends of the frame structure 1 covering said openings, cooling coils in the housings, and fan means in the frame structure between the generator and motor for circulating air in a closed path through the ducts between the generator stator core and'the frame structure, the housing'atthegenerator end of the frame structure, and back throughfthe generator, and for circulating air in a separate closed path through the outer ducts betweenthe motor stator core and the frame structure, the housing at the motor end of the frame structure, and back through the inner ducts between the motor stator core and the frame structure and through the motor. 7 e

9. A motor-generator set comprising a frame structure, an electric generator and an electric motor supported in the frame structure and having a common shaft, the generator andthe motor each having a rotor member mounted on the shaft, the generatorrotor having axial air passages therethrough, the generatorhaving a stator core carrying windings,- said stator core being I mounted in the frame structure to provide axial ducts for ventilating air between the stator core and the frame structure, the motor having a stator core carrying windings, means for mounting the motor stator core in the frame structure with its periphery spaced from the frame structure, longitudinal barrier members disposed in the space between the motor stator core and the frame structure to divide the space into radially inner and outer parallel, axial ducts for ventilating air, fan means on the shaft between the generator and motor for circulating air in separate paths through the generator and motor and said ducts, the frame structure having radially spaced openings for air at the ends thereof, balile means adjacent the openings at the generator end of the frame structure for directing air flowing through the radially inner openings into the axial passages of the generator rotor and for separating said air from the air flowing through the radially outer openings and the axial ducts between the generator stator core and the frame structure, and balfie means at both ends of the motor for directing air flowing through the radially inner'openin'gs at the motor end of the frame structure into the inner of said parallel ducts and for directing said air into the fan means and separating it from air flowing through the outer openings at the motor end'of the frame structure and the outer of the parallel ducts.

FRANCIS J. JOHNS.

HENRY J. OWENS.

REFERENCES errsn The following references are of record in the file of this patent:

UNITED STATES PATENTS Abbott Dec. 20, 1949 

